Similar body composition, muscle size, and strength adaptations to resistance training in lacto-ovo-vegetarians and non-vegetarians

There is a popular belief that meat consumption is necessary to optimize adaptations to strength training (ST), but evidence to support this hypothesis is scarce. Therefore, this study aimed to compare ST adaptations in lacto-ovo-vegetarians (LOV) and non-vegetarians (NV) with adjusted protein intake per meal. Sixty-four LOV and NV performed 12 weeks of ST and were instructed to ingest at least 20 g of protein in each main meal during the experimental period. Quadriceps femoris muscle thickness (QFMT), knee extension one-repetition maximum (1RM), and isometric peak torque (PT), as well as participants' body composition were assessed before and after the intervention. Dietary intake was assessed throughout the study. After 12 weeks, similar increases in QFMT (LOV: 9.2 +/- 5.4; NV: 5.5 +/- 8.1 mm), knee extension 1RM (LOV: 24.7 +/- 11.1; NV: 21.6 +/- 9.8 kg), and PT (LOV: 29.8 +/- 33.4; NV: 17.5 +/- 19.4 N m) and lean body mass (LOV: 1.3 +/- 0.9; NV: 1.4 +/- 1.4 kg), alongside a decrease in body fat mass (LOV: -0.5 +/- 1.6; NV -0.8 +/- 1.6 kg) were observed in both groups at the end of the training period (p < 0.05). LOV had lower protein consumption than NV throughout the study (p < 0.05), but participants reached intake of at least 1.2 g of protein/kg/day during the experimental period. In conclusion, LOV and NV displayed similar improvements in muscle mass, strength, and in body composition after 12 weeks of ST, suggesting that meat consumption and higher protein intake in NV did not bring about further benefits to early adaptations to ST. This study was registered in Clinical Trials (NCT03785002) on 24 December 2018.